Improvements, in or relating to magnets



July 21, 1936. A. REHMANN l 2,048,222

IMPROVEMENTS IN OR RELATING TO MAGNETS Filed oct. 19, 1952 wvimwwmm F/g.

i 1`I .i I l 10 il Patented July 2l, 1936 UNITED STATES PATENT OFFICE IMPROVEMENTS, IN

MAGNE 0B RELATING T0 Krefeld, Germany Application October 19, 1932, Serial No. 638,601 In Germany October 8, 1931 2 Claims.

'lhe present invention relates to magnets, which at the present time are normally produced from steel alloys by rolling, forging, or casting. According to the invention the cores or pole pieces of magnets or both are produced by sintering a mass of finely powdered material, the invention also covering cases in which magnets are partly manufactured by sintering. The invention is especially applicable to the manufacture of magnets of elliptical type, for instance, magnets for loud speakers, which hitherto are diilicult to produce. The magnetic qualities of magnets manufactured as above are highly increased.

It is particularly suitable for the purpose to complete the sintering of the pole-pieces themselves by a sintering process and then to eect the sintering of the pole-pieces with the magnet by a second process. 'I'he process may be varied in such a manner that' pole-pieces of solid or laminated material are combined with the sintered body into a complete magnet. The combining of the pole-pieces with the sintered body may be effected during the sintering process or even after sintering, for instance, by shrinking on, welding or soldering.

The invention may be clearly understood and readily carried into effect with reference to th accompanying drawing in which: i

Figure 1 -is a longitudinal section of a magne with sintered pole pieces.

Figure 1a is a plan view of the magnet shown in Fig. 1.

Figure 2 is a longitudinal section of a device for pressing and sintering of pole pieces.

Figure 3 is a part of a device in longitudinal section for the pressing and sintering of pole pieces.

Figure 4 is a longitudinal section of a high frequency electric furnace with a mould adapted to form magnets taken along line l-I of Fig. 4a.

Figure 4a is a detail sectional view of the Figure 4 showing the magnet with the moulding core I8, taken along line I--I of Fig. 4.

Referring first to Figure 1, I and 2 represent the sintered pole pieces, 3 indicates the cast body of the corresponding part of the magnet.

In Figlne 2, Il illustrates the pressing stamp with an annular groove 5, 6 the inner-pole and l the outer-pole, 8 an inserted annular rib, adapted to form the air gap, 9 and I0 represent the moulding members. The manufacture of pole pieces according to Figure 2 is carried out in the following manner. The mould 9, I0 as illustrated in the drawing ls filled with powdered material and the mass is then tamped and com- (Cl. F-21) pressed by the tamper 4 and sintered in the mould by the application of heat.

In Figure 3, I I represents the ram. I3a to I3e represent a group of outside pole rings of finely divided material, which are enclosed by moulding members I2a to I2f, I4 and I5. 'I'he manufacturing of the articles is the same as above described.

In Figure 4, I1, I8 and I9 are moulding members, I6 a ring adapted to shape the air gap, 20 the ram, 2i a cylinder, 22 a carbon mass, 23 a fused silica tube, 24 a coil of flattened copper pipe with electric connection 25 at either end of the coil, 26 a refractory block, 21 an iron sheet.

The Figure 4a illustrates a construction of the moulding core I8 and its arrangement in the magnet. As it is shown the core I 8 is divided into several parts for instance Isa, IBb, I 8c and Ild. Two of them I8b and Id are larger than the other parts of the core as illustrated in the drawing and form holes at the bottom of the magnet. The cores Ibb, I8d and the moulding part I9 are all of one piece. This construction 1s advantageous as the iron parts of the mould have to withstand a high pressure exercised by the ram on the mould lled with the powder of magnetical material. The cores |817 and I8d can be removed after the magnet is sintered. Thereafter the cores I8a and I8c can be taken out through the holes at the bottom of the magnet. The process of producing the magnets can be carried out in the following manner. The mould constituted by I6, I1, IB and I9 is partly filled with nely powdered material consisting for instance of cobalt, tungsten, chromium, molybdenum and iron with carbon particularly in the limits of 5-50% Co, 1-10% W. lil-90% Fe with 0.5-7% carbon.

Since the pole shoes should consist of iron or a material with high permeability, the whole mould is not completely lled with the material above mentioned but only the lower part. The upper part of the mould is then lled with finely divided iron. The whole mass is thereafter tamped and sintered by subjecting the mould to a heat-treatment, for instance by subjecting the mass to a pressure of about 34,000 pounds per square inch and high frequency eddy currents of electricity at a rate of 4-6 kilovolt-amperes. At the end of the process the current is turned oif and the mould allowed to cool.

I claim:

1. Method of producing magnets by joining the pole pieces with the magnet-body comprising the forming and sintering of the pole pieces and sepu :rated therefrom the producinx of the magnet bodyendthejolnlnzotthepolepleeelwlththe magnet by heating the parte in o. furnace and ahnulteneouslypreuinzthemmether.

2. Method of producing magnets comprising the forming of the meznetbodyby ramping end compressing nely powdered meterlelinomould.

the forming of the pole pieces thereafter by llinguptbenme mouldwlthemueotnnelypovdered msteril. end by tamplnz end eompreseinl this mns, :interina the whole man by bestial and by simultaneously oompreninz it 1n o mrnice AUGUST RIHIIANN. 

